1. Field of the Invention
The present invention relates to a calibrating device for a balance including a load receiving unit for loads to be weighed, a load measuring unit and a lever mechanism serving for the force transmission between the load receiving unit and the load measuring unit, wherein the lever mechanism is coupled to the load receiving unit through a coupling area on an input side and to the load measuring unit through a coupling area at an output side, and wherein the lever mechanism further includes an additional coupling area, separate from the coupling areas on the input and output sides, for releasably coupling a calibrating force which is uncoupled during the normal weighing operation.
2. Description of the Related Art
In a calibrating device of the above-described type known from DE 26 09 560 A1, an approximately V-shaped receiving means for a calibrating weight is provided in a lever serving for the stepping down of the force between the load receiving unit and the load measuring unit. For carrying out the calibration, a calibrating weight is placed in the interior of the balance in the receiving means, wherein the calibrating weight is uncoupled from the lever during the normal weighing operation. In order to ensure a calibration of the balance which is as accurate as possible, the receiving means is arranged over the entire weighing area of the balance with a relatively small calibrating weight on the lever in such a way that the force of the calibrating weight acts fully on the load measuring unit, i.e., without stepping down of the force.
For utilizing the absolute accuracy of a balance achievable as a result of resolution, which may be 0.1 g or even higher when using a 32 kg weighing cell, it is necessary when using the known calibrating device to place the calibrating weight, in longitudinal direction of the lever as well as in a direction perpendicular to the longitudinal direction, in the receiving means with a positional accuracy in the order of magnitude of 10.sup.-3 mm on the longitudinal axis of the lever. For ensuring such a positional accuracy, an extremely complex mechanism is required for releasably coupling the calibrating weight. If the calibrating weight is coupled with less accuracy, the absolute accuracy of the balance determined by the resolution cannot be realized.